diff options
Diffstat (limited to 'common/recipes-kernel/linux/linux-yocto-4.9.21/0006-x86-spectre_v1-Disable-compiler-optimizations-over-a.patch')
| -rw-r--r-- | common/recipes-kernel/linux/linux-yocto-4.9.21/0006-x86-spectre_v1-Disable-compiler-optimizations-over-a.patch | 84 |
1 files changed, 84 insertions, 0 deletions
diff --git a/common/recipes-kernel/linux/linux-yocto-4.9.21/0006-x86-spectre_v1-Disable-compiler-optimizations-over-a.patch b/common/recipes-kernel/linux/linux-yocto-4.9.21/0006-x86-spectre_v1-Disable-compiler-optimizations-over-a.patch new file mode 100644 index 00000000..a8632983 --- /dev/null +++ b/common/recipes-kernel/linux/linux-yocto-4.9.21/0006-x86-spectre_v1-Disable-compiler-optimizations-over-a.patch @@ -0,0 +1,84 @@ +From d98751217028054a791c98512d1ed81d406f55da Mon Sep 17 00:00:00 2001 +From: Dan Williams <dan.j.williams@intel.com> +Date: Thu, 7 Jun 2018 09:13:48 -0700 +Subject: [PATCH 06/10] x86/spectre_v1: Disable compiler optimizations over + array_index_mask_nospec() + +commit eab6870fee877258122a042bfd99ee7908c40280 upstream. + +Mark Rutland noticed that GCC optimization passes have the potential to elide +necessary invocations of the array_index_mask_nospec() instruction sequence, +so mark the asm() volatile. + +Mark explains: + +"The volatile will inhibit *some* cases where the compiler could lift the + array_index_nospec() call out of a branch, e.g. where there are multiple + invocations of array_index_nospec() with the same arguments: + + if (idx < foo) { + idx1 = array_idx_nospec(idx, foo) + do_something(idx1); + } + + < some other code > + + if (idx < foo) { + idx2 = array_idx_nospec(idx, foo); + do_something_else(idx2); + } + + ... since the compiler can determine that the two invocations yield the same + result, and reuse the first result (likely the same register as idx was in + originally) for the second branch, effectively re-writing the above as: + + if (idx < foo) { + idx = array_idx_nospec(idx, foo); + do_something(idx); + } + + < some other code > + + if (idx < foo) { + do_something_else(idx); + } + + ... if we don't take the first branch, then speculatively take the second, we + lose the nospec protection. + + There's more info on volatile asm in the GCC docs: + + https://gcc.gnu.org/onlinedocs/gcc/Extended-Asm.html#Volatile + " + +Reported-by: Mark Rutland <mark.rutland@arm.com> +Signed-off-by: Dan Williams <dan.j.williams@intel.com> +Acked-by: Mark Rutland <mark.rutland@arm.com> +Acked-by: Thomas Gleixner <tglx@linutronix.de> +Acked-by: Linus Torvalds <torvalds@linux-foundation.org> +Cc: <stable@vger.kernel.org> +Cc: Peter Zijlstra <peterz@infradead.org> +Fixes: babdde2698d4 ("x86: Implement array_index_mask_nospec") +Link: https://lkml.kernel.org/lkml/152838798950.14521.4893346294059739135.stgit@dwillia2-desk3.amr.corp.intel.com +Signed-off-by: Ingo Molnar <mingo@kernel.org> +Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> +--- + arch/x86/include/asm/barrier.h | 2 +- + 1 file changed, 1 insertion(+), 1 deletion(-) + +diff --git a/arch/x86/include/asm/barrier.h b/arch/x86/include/asm/barrier.h +index 78d1c6a..eb53c2c 100644 +--- a/arch/x86/include/asm/barrier.h ++++ b/arch/x86/include/asm/barrier.h +@@ -37,7 +37,7 @@ static inline unsigned long array_index_mask_nospec(unsigned long index, + { + unsigned long mask; + +- asm ("cmp %1,%2; sbb %0,%0;" ++ asm volatile ("cmp %1,%2; sbb %0,%0;" + :"=r" (mask) + :"g"(size),"r" (index) + :"cc"); +-- +2.7.4 + |